Month: November 2018

Trim string starting suffix

Today I wanted to remove, from a string, the substring starting with a specified string.

For a line of code with a comment started with #, I wanted to remove everything starting at #, so the line “line with #comm#ent” should become “line with “.

The test for this is:

func TestRemoveFromStringAfter(t *testing.T) {
   tests := []struct {
      input,
      after,
      expected string
   }{
      {
         input:    "line with #comm#ent",
         after:    "#",
         expected: "line with ",
      },
      {
         input:    "line to clean",
         after:    "abc",
         expected: "line to clean",
      },
      {
         input:    "line to clean",
         after:    "l",
         expected: "",
      },
      {
         input:    "",
         after:    "",
         expected: "",
      },
      {
         input:    " ",
         after:    "",
         expected: " ",
      },
   }

   for i, test := range tests {
      result := RemoveFromStringAfter(test.input, test.after)
      if result != test.expected {
         t.Fatalf("Failed at test: %d", i)
      }
   }
}

I tried to use TrimSuffix and TrimFunc from the strings package, but they weren’t getting me where I wanted. Then, all of a sudden, it stroke me: a string can be treated as a slice and a subslice is what I need. A subslice which ends right before the position of the suffix I give.

So I take the position of the suffix and extract a substring of the input string:

func RemoveFromStringAfter(input, after string) string {
   if after == "" {
      return input
   }

   if index := strings.Index(input, after); index > -1 {
      input = input[:index]
   }

   return input
}

Test multiple PHP exceptions

There are cases when you have a base exception class which is extended by other exceptions. For a package called User, you could have a UserException which is inherited by UserNotFoundException, UserPasswordException and so on.

The base exception of your package allows you to catch any thrown exception from inside the package.

So there’s a base exception, a specific one and the service using them:

class BaseException extends Exception
{
}

class NoItemsException extends BaseException
{
}

class Service
{
    /**
     * @param array $items
     * @throws NoItemsException
     */
    public function save(array $items)
    {
        if (count($items) === 0) {
            throw new NoItemsException('Nothing to save');
        }
    }
}

And you want to catch all package exceptions:

$service = new Service();
try {
    $service->save([]);
} catch (BaseException $e) {
    die($e->getMessage());
}

And a test for the case:

class ServiceTest extends TestCase
{
    /**
     * @expectedException NoItemsException
     */
    public function testSaveWithNoItems()
    {
        $service = new Service();
        $service->save([]);
    }
}

How do you make sure NoItemsException extends BaseException?
With the above test, if you change NoItemsException to extend Exception instead of BaseException, the test will still pass, but the behaviour won’t be the expected one, because you won’t be catching the exception anymore:

Fatal error: Uncaught NoItemsException: Nothing to save... in /src/Service.php on line 20

NoItemsException: Nothing to save... in /src/Service.php on line 20

Your test must explicitly test both exceptions:

class ServiceTest extends TestCase
{
    public function testSaveWithNoItems()
    {
        $service = new Service();

        try {
            $service->save([]);
            $this->fail('No exception thrown');
        } catch (\Exception $e) {
            $this->assertInstanceOf(BaseException::class, $e);
            $this->assertInstanceOf(NoItemsException::class, $e);
        }
    }
}

QA tools for Go apps in CI/CD

Go Meta Linter is a great tool to run code quality checks including vet, static analysis, security, linting and others. I’ve used it a few times, enjoyed it, and I’ve built a basic setup to include it into CI/CD, along with the unit tests execution.

All you need is Docker and a Docker images repository like Docker Hub. You’ll build an image to run the tools in, push it to your repository, then pull it on your CI/CD machine and run a container from it, as simply as:

docker run -ti --rm \
    -e PKG=github.com/andreiavrammsd/dotenv-editor \
    -e CONFIG=dev/.gometalinter.json \
    -v $PWD:/app \
    yourdockerusername/go-qa-tools \
    make

(later edit: I archived the example package)

Of course, it can be integrated into a service like Travis:

sudo: required

language: minimal

install:
- docker pull andreiavrammsd/go-qa-tools

script:
- docker run -ti -e PKG=github.com/andreiavrammsd/dotenv-editor -e CONFIG=dev/.gometalinter.json -v $PWD:/app andreiavrammsd/go-qa-tools make

See the full Go QA tools setup on GitHub.